The Laser Heterodyne System is

a complete, easy-to-use system for

calibrating and characterizing laser

frequency standards. The system allows

for characterization of both short- and

long-term laser behavior using the highly

accurate and sensitive optical heterodyne

technique. The setup can be easily re-

configured to meet the requirements

of special applications, or expanded to

accommodate multiple lasers.

Basic System Components

• 0.6 m x 0.9 m optical breadboard

• (2) broadband HR mirrors and (1) broadband beam combiner with kinematic mirror mounts

• Focusing lens with 3-axis translation stage

• Linear polarizer, λ/4 and λ/2 waveplates with rotary mounts, and adjustable aperture

• Acousto-optic modulator for optical isolation

• 1 GHz photodetector with lo-noise high-gain amplifier, power supplies, lo-pass filters, and rf power splitter

• Agilent 53181A frequency counter with IEEE-488 interface and 1.5 GHz option

• Notebook computer with IEEE-488 interface and Windows XP operating system

• LaserCal data acquisition and analysis software

Laser Heterodyne SystemElectro-Optics, Inc.

Winters

The Laser Heterodyne System is used to calibrate and

characterize primary (e. g. iodine-stabilized) and secondary

(e. g. 2-mode polarization-stabilized or Zeeman-stabilized)

laser frequency standards. It includes all the optics and

electronics required to generate and measure an optical

heterodyne signal produced by the “beating” of two

frequency-stabilized lasers. While primarily designed for

use with 633 nm He-Ne lasers, it can also be used to compare

frequency-stabilized lasers in other parts of the visible

spectrum.

The Laser Heterodyne System includes beam steering

and beam combining optics to physically overlap the output

beams of a reference laser and a laser-under-test (LUT).

A focusing lens steers the overlapped beams onto a high-

bandwidth, high-gain avalanche photodetector (APD), which

generates an electrical signal representing the frequency

difference of the two lasers. Waveplates, a polarizer, and

electrical filters can be used in various combinations to isolate

individual modes of two-mode lasers. An acousto-optic

modulator provides isolation from optical feedback, ensuring

stable operation of the reference laser and the LUT.

Frequency measurements are made with an Agilent

53181A frequency counter linked to a notebook computer

via an IEEE-488 interface. LaserCal data acquisition and

analysis software records frequency data and calculates Allan

Variances and matrix frequency differences. Results can be

output to Windows-compatible printers or saved to disc.

Data files are written in a simple format for easy exportation

to other applications for further manipulation and analysis,

if desired.

A basic heterodyne system is built on a 0.6 m x 0.9 m

optical breadboard and accommodates a reference laser

and one LUT. The system is highly modular and can be

easily modified to meet special requirements, and it can be

expanded to accommodate multiple LUTs with the addition

of a few standard components.

WINTERS ELECTRO-OPTICS, INC. • 7160 Nimbus Road • Longmont, Colorado, USA 80503Tel: 303-651-6951 • FAX: 303-651-7584 • www.winterseo.com

Layout of the basic heterodyne system showing the optics, optical mounts, acousto-optic modulator, and avalanche photodetector (APD). System components not shown include the notebook computer, frequency counter, IEEE-488 interface, power supplies, rf

filters, and rf power splitter. (Reference laser, laser under test, and spectrum analyzer are not included in the basic system.)

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BEA

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Helium

Neon Laser

1 milliw

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CLA

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PRO

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Reference Laser(Model 100 Iodine-Stabilized He-Ne)

Laser Under Test(LUT)

Beam Combiner

HR Mirror

Waveplate

Waveplate

Polarizer Lens

Acousto-opticModulator

AdjustableAperture

APD

HR Mirror

3-axis stage with focusing lens